Preliminary studies show that trifluoperazine, which inhibits Ca + + calmodulin mediated functions, blocks glucose and glyceraldehyde-stimulated insulin release but not IBMX-induced release. This suggests a calmodulin-dependent step in stimulus-secretion coupling for glucose subsequent o the trioses but prior to the elevation of cytosol Ca + +. As IBMX-stimulated release is unaffected, the process of exocytosis appears to be calmodulin-independent. The aims of the research are to study the role of calmodulin, a Ca + + dependent regulator protein, in glucose-stimulated insulin release. 1. Information can be gained using trifluoperazine and other tricyclic antipsychotic agents, which specifically block the acitivty of calmodulin. This will include measurements of insulin release due to selected secretagogues, under both static and perifusion conditions, in the presence of absence of trifluoperazine and the other agents. 2. As trifluoperazine should block the ability of glucose to raise cytosol Ca + + levels, a detailed study of its effects on Ca + + handling will be performed. 45 Ca + + efflux, Ca + + influx and total Ca + + content of islets will be measured under stimulated and inhibitor-treated conditions, as will the simultaneous bidirectional Ca + + fluxes in islets. 3. Islet content of calmodulin will be measured under conditions of changed insulin release responsiveness. For examples, islets in tissue culture which lose their cyclic AMP response to glucose - a response though to be calmodulin dependent; islets from animal models with defective responses to glucose; islets from rats in the late stages of pregnancy and from hyperfed rates; studies will also be performed on insulinoma cells (which behave as though they have been treated with trifluoperazine). 4. Calmodulin-dependent enzymes will be sought - particularly those thought to be relevant to insulin release. These include adenylate cyclase, phosphodiesterase, Ca + + ATPase and Ca + + dependent protein kinase. 5. Ca + + transport into islet stores will be studied and correlated with Ca + + ATPase, Ca plus plus dependent potein kinase and cyclic AMP-dependent protein kinase activity.